1. Field
Example embodiments relate to a transistor and a method of manufacturing the same. Other example embodiments relate to a semiconductor device including a transistor and a method of manufacturing the same.
2. Description of the Related Art
Transistors are widely used as switching devices or driving devices in the field of electronic equipment. In particular, because thin film transistors (TFTs) may be fabricated on a glass substrate or a plastic substrate, TFTs are mainly used in flat panel display apparatuses (e.g., liquid crystal display (LCD) devices) and organic light emitting display (OLED) apparatuses.
In order to achieve the desired operational properties of transistors, attempts have been made to utilize an oxide layer having high carrier mobility (e.g., a ZnO-based material layer) as a channel layer. The above method is mainly applied to TFTs for the flat panel display apparatuses.
In the transistors having the oxide layer as the channel layer (hereinafter, referred to as “conventional oxide transistors”), it may be difficult to control a threshold voltage. If a silicon layer is used as the channel layer, n-channel metal-oxide semiconductor (NMOS) transistors and p-channel metal-oxide semiconductor (PMOS) transistors may be more easily fabricated by changing the kind of elements doped in the channel layer. In addition, the threshold voltage may be controlled by adjusting the concentration of the doped elements. According to the oxide material transistor, it may difficult to control the threshold voltage by the doping due to a self-compensation.
The channel layer formed of the oxide material may be primarily formed of an n-channel layer. The conventional oxide transistors are mainly depletion mode transistors of which the threshold voltage is less than 0 volts.